Muffler internally coated with highly refractory fibers



Feb. 8, 1966 G. SLAYTER ETAL 3,233,697

MUFFLER INTERNALLY COATED WITH HIGHLY REFRACTORY FIBERS Original FiledJune 7, 1960 2 Sheets-Sheet 1 INVENTORS GAMES Smvrm, Roam-r G Passe-u. &

BY Mann A. Moran/v Arron/vars Feb. 8, 1966 e. SLAYTER ETAL 3,233,697

MUFFLER INTERNALLY COATED WITH HIGHLY REFRACTORY FIBERS Original FiledJune '7, 1960 2 Sheets-Sheet 2 INVENTORS GAMES SLAYrER, Panzer 6. Russsu&

Z WILLARD L. Manamv A 7 Rfi/E Y5 United States Patent 3,233,697 MUFFLERINTERNALLY COATED WITH HIGHLY REFRACTORY FIBERS Games Slayter, Newark,and Robert G. Russell, Granville, Ohio, and Willard L. Morgan,Spartanhurg, S.C., assignors to Owens-Corning Fiberglas Corporation, acorporation of Delaware Original application June 7, 1960, Ser. No.34,408, now Patent No. 3,109,511, dated Nov. 5, 1963. Divided and thisapplicatiouMay 6, 1963, Ser. No. 278,330

2 Claims. (Cl. 181-42) This application is a division of our copendingapplication Serial No. 34,408, filed June 7, 1960, now Patent No.3,109,511.

This invention relates to an improved muffling system and moreparticularly to a vehicle muflling system in which components are linedwith highly refractory fibers.

Present mufilers include casings or walls of one or more wraps of steelwhich enclose a plurality of internal steel battles to mutile the soundof the engine and exhaust gases. These mufflers are subjected toconditions which cause the casings to be attacked with the result thatthe mufilers are relatively short lived. For example, particularly inwinter and on short trips, liquids of an acidic nature from the enginewill deposit on and attack the interior surface of a muffler casing. Onlong trips the mufller casing also tends to become very hot, the gaseswithin the casing often being over 1600 F. under normal operatingconditions and may be substantially higher than this if a spark plug isnot functioning with the result that a cylinder exhausts a mixture ofair and raw fuel into the exhaust system where it burns partially. Oilexpelled from the engine through the exhaust system, and deposited inthe mufller, may also smolder and thereby further increase interiortemperatures. Elevated mufiler casing temperatures increase the rate atwhich the casing oxidizes or rusts.

There is also reason to believe that conventional mufflersmay increasethe amounts of certain deleterious contaminants in exhaust gases.Available evidence indicates that exhaust gases in contact with hot ironor steel undergo a reaction which increases the amounts of olefins inthe gases. This reaction can occur in conventional muffiing systems,wherever exhaust gases contact hot steel or oxidized cast ironcomponents of an exhaust system.

In addition, the bare metal walls of conventional muf- ,flers andmufiling systems extract heat rapidly from the exhaust gases, thuscausing the gases to cool rapidly. Such cooling prevents secondarycombustion in the exhaust system that might otherwise consume at leastpart of the carbon monoxide and olefins in the exhaust gases. In presentmufiiing systems, secondary combustion is very rare and may onlyoccur athigh operating speeds when raw fuel and air flow through the exhaustsystem.

The present invention relates to a muffling system having a linedcomponent and to an insulating liner which overcomes the above-discusseddisadvantages of existing muffling systems. The liner is preferably madeof highly refractory fibers held together by a suitable binder, the

. liner being located near the inner surface of the component, betweenit and the exhaust gases. There is a much smaller tendency forcondensation to occur with the new exhaust system because the exhaustgases are kept out I of contact with the cold walls of the system, andbecause the linear remains hot longer after the engine is stopped.

Any such liquid that does condense, as in winter when the engine is notoperated for a long enough period to heat the liner sufficiently, willeventually evaporate in the tern components at much lower temperaturesby comparison with conventional systems, the walls being approximately300 F. or less when the exhaust gases are 1600 F. when a liner onlyone-half inch thick is used. The relatively cool walls thus tend tooxidize, rust, and warp to a much smaller degree than formerly and nospecial steels are required for the mufiler components as mightotherwise be necessary. In addition, the new liner prevents contactbetween the exhaust gases and the steel or cast iron walls of the linedexhaust system component and thus prevents an increase in the amount ofolefins which otherwise occurs. Reduction in heat loss from the manifoldunder the hood also reduces driver discomfort in the summer when themaniold is lined in accordance with the invention. Because theinsulating liner prevents rapid extraction of heat from the exhaustgases to the mufiier walls, the exhaust gases remain at much highertemperatures and can undergo secondary combustion in the system. Theliner also provides an effective surface in contact with whichcombustion of the gases can proceed. To aid in secondary combustion, aircan be added to the exhaust gases at a point upstream of the mufiier toprovide additional oxygen for combustion of the remaining fuel in theexhaust gases.

It is, therefore, a principal object of the invention to provide animproved muflling system including an interior, insulating liner.

Another object of the invention is to provide an exhaust system wherefewer deleterious substances are present in the exhausted gases.

Still another object of the invention is to provide a muffler having alonger life than those presently known in the art.

Yet another object of the invention is to provide a muffling system inwhich the exhaust gases are maintained at higher temperatures so thatadditional, secondary combustion can occur therein.

Other objects and advantages of the invention will be apparent from thefollowing detailed description of a preferred embodiment thereof,reference being made to the accompanying drawings, in which:

FIG. 1 is a somewhat schematic view, with parts broken away and parts incross section, of an engine and a muifling system embodying theprinciples of the inventron;

FIG. 2 is a greatly enlarged view in cross section of a muffler of thesystem shown in FIG. 1;

FIG. 3 is a view in transverse cross section taken along the line 3-3 ofFIG. 2;

FIG. 4 is a view in perspective of a liner segment used in the mufiiingsystem and the mufller of FIGS. 1-3;

FIG. 5 is a view in vertical cross section of a mold for making thesegment shown in FIG. 4;

FIG. 6 is a somewhat schematic view in cross section of modifiedapparatus for lining mufiling systems; and

FIG. 7 is a view in cross section of further modified apparatus forlining mufiling systems.

Referring to FIG. 1, an eight cylinder engine is indicated at 10, thecylinders of Which are connected to a mufili-ng system indicatedgenerally at 12, although the two banks of cylinders can alternately beconnected to separate mufiling systems. The system 12 includes linedmanifolds 14, a lined connecting pipe 15, a lined' exhaust pipe 16, alined mufiler 18, and a tailpipe 20 which can be lined or not.

The mufiler 18 (FIGS. 2 and 3) includes a casing 22 comprising two halfsections 24 and 26 which can be bolted together at flanges 28 and 30(FIG. 3) extending longitudinally thereof. Suitable conecting pipes 32and 34 (FIG. 2) are afiixed to end walls of the casing 22 for connectionwith the exhaust pipe 16 and the tailpipe 20, in a maner well known inthe art. Within the casing 22 is a perforate metal tube 36, which isspaced from the casing 22 by suitable spacers 38, reinforced cementrings being suitable for this purpose. Within the perforate tube 36 is acylindrical liner 40 made of a plurality of circular or ring segments 42which are placed in coaxial, end-to-end relationship and preferablycemented together by a ceramic band. The outer diameter of the segments42 is large enough to enable them to be held tightly within the tube 36and the inner diameter of the segments 42 is sufiicient to form apassage for exhaust gases from the engine 10. The walls of the segments42 are at least A" thick to provide reasonable strength and have beenmade in thicknesses up to approximately 1 /2 of either porous ornon-porous ceramic of the type described below.

The segments 42 are integral, porous bodies containing highlyrefractory, titania fibers, and are self-sustaining within the tube 36,requiring no internal wall or support within the bodies. The liner 40prevents attack of the muffler casing -by keeping any corrosive liquidsin the exhaust gases out of contact therewith. The titania ceramic isalso resistant to acids, to high temperature steam, and to the variouscorrosive contaminants within the exhaust gases. The liner 40 also actsas an extremely good insulator with the result that the temperature ofthe casing 22 seldom exceeds 300 F., even when the exhaust gases are at1600 F. or higher. In addition, the exhaust gases are kept out ofcontact with the casing 22 to prevent an increase in the amount ofolefins which might otherwise result. Finally, the exhaust gases arekept at a higher temperature within the exhaust system due to theinsulating effect of the liner 40 that additional combustion of thesegases can take place in order to reduce the amount of deleteriouscontaminants therein. For this purpose, additional air can be added tothe exhaust system through an air pipe 44 (FIG. 1), which is conected tothe exhaust pipe 16. The air can be supplied by a small blower 46 or,duringmovemerit of the vehicle, by an air scoop. I

The segments 42, a single one of which is shown in perspective in FIG.4, have been made from a mixture of 87 grams crystalline titania fibersfrom /4" to /2" long, 20 grams of wood sawdust, 25 grams ofMontmorillonite and 13 grams of powdered soda-lime glass. This mixturewas combined with sufficient water to make a mortar or paste of fibrouspellets which were then pressed into a mold the size and shape of thesegment 42 and fired at 2500" F. to cause the soda-lime glass andMontmorillonite to form a binder for the titania fibers and to cause thesawdust to burn out and leave a porous body. The resulting bodyconsisted essentially to 70% titania, 20% Montmorill-onite, and sodalimeglass. By volume, the body contained approximately 70% air, titaniafibers, and 10% binder (Montniorillonite and soda-lime glass), with anapparent density of approximately 70 pounds per cubic foot. Segments 1"thick show only slight resistance when air is blown through them. I

While the segments 42 have been made in a metal mold having an annular,tapered cavity, it has been found that the material is difficult toremove therefrom preparatory to firing. For this reason, the segments 42are preferably made in a mold 44 shown in FIG. 5. The mold 44 includesan outer cylindrical wall 46 and an end wall 48 of paper, cardboard, orother organic material which will burn away at a temperature below thefiring temperature of the segment material. A metal rod 50 which isconcentric of the mold 44 extends through the end wall 48 to form anannular cavity with the end wall 48 and the cylindrical wall 46, thecavity having a shape and size similar to those of the segment 42. Afterthe liner material is placed in the cavity and tamped therein, the metalrod 50 is removed to leave the green liner and the walk 46 and 48 whichare fired as a unit, the Walls 46 and 48 burning away, with only thefired, hardened segment 42 then remaining. With this arrangement, theliner material need not be removed from the mold prior to firing.

The porous liner 49 not only provides the advantages outlined above, butalso constitutes an effective acoustic material to absorb sound andmuffle the noise of the exhaust gases and engine. The perforate tube 36further enhances the acoustical absorption properties of the muffler 18,particularly for sound of lower frequency. However, the liner 40 can bemade with a larger diameter and placed immediately adjacent the casing22, with the porous tube 36 eliminated, to provide substantially as goodsound absorption. It is desirable that the muffler have a volume aboutten times the volumetric displacement of the engine cylinders from anacoustical standpoint.

In accordance with the principles of the invention, it also has beendiscovered that the liner material can 'be employed in the manifold 14and the exhaust pipe 16 to maintain the temperature of the exhaust gasesseveral hundred degrees higher than otherwise and also to keep theexhaust gases separate from the steel or iron of which the manifold 14and the exhaust pipe 16 are made to pre vent reaction on the surfacethereof. The manifold 14 and the exhaust pipe 16 are also maintained atcooler temperatures by being insulated from the exhaust gases, andtemperatures under the hood are decreased. Because the temperatures ofthe lined exhaust system components are much lower than in conventionalexhaust systems, the manifold 14 can be made of welded or fabricatedsheet steel, the manifold 14 in this case comprising a cylindrical metaltube 52 and shorter connecting tubes 54 of welded sheet steel.Previously, it was necessary in most instances to cast the manifold 14which, because of its high temperature, had considerable tendency towarp, making the use of fabricated steel impractical.

The manifold 14 and the exhaust pipe 16 have been lined with segmentssimilar to the segments 42, but of smaller diameter. However, where themanifold 14 or the exhaust pipe 16 is of relatively complicated shape,the liner can be applied to these components in the form of a thickcoating on the interior walls thereof. Because sound absorption is not aconsideration in the manifold 14 and the exhaust pipe 16, the liner inthis casen'eed not be porous, and the sawdust or other material formingvoids in the final product need not be employed or can be employed to alesser degree. The refractory f bers in the liner material preferablyare shorter than those used in the liner 40 to enable the liner materialto be more easily applied to the interior of the com onent After theliner material is applied it can be fired in the mufiling systemcomponents by passing highly heated gases therethrough to provide theproper firing temperatures therein without excessively heating the outerwalls of the components.

A thick layer of the coating material can be applied to the innersurfaces of the manifold 14 and the exhaust pipe 16 with the apparatusshown in FIG. 6. In this instance, the binder materials and the titaniafibers can be supplied separately, and titania powder can be added toincrease the strength of the liner. The apparatus, indicated generallyat 56, moves from left to right in FIG. 6 through the exhaust pipe 16,for example, which preferably is concommitantly rotated. Titania powdercan first be supplied to the interior of the pipe 16 through a supplyline 58 and the binder material then supplied through a second supplyline 60, with the titania fibers then being supplied to the surface ofthe binder material through a third supply tube 62. The binder andtitania also can be supplied through a single supply line 'as a premixedaqueous paste by means of air pressure. The liner material which is nowdeposited on the interior of the tube 16 is subsequently spread evenlyby means of a spreader 64 which is in the form of a flexible cone or aplurality of flexible arms. In either case the spreader 64 is spacedfrom the inner surface of the pipe 16 by means of spacers 66 whichdetermine the thickness of the liner.

A modified liner applicator 68 is shown in FIG. 7 and includes an outerpassage 70 through which the binder or coating material is sprayedthrough an annular nozzle 72 which also can be a plurality of individualnozzles. The titania fibers are subsequently sprayed onto the wetcoating material by means of an inner passage 74 through which thetitania fibers are blown, being deflected to the wall of the pipe 16 bya deflector 76. Again, the titania fibers and the binder material can besupplied through a single spray passage.

Other binders and other highly refractory fibers, such as zircon andzirconia fibers, have been found to be suitable for use in a linedmufiiing system according to the invention. The fibers employed must beof a highly refractory nature, capable of withstanding temperatures of1800 F. and preferably 2600 F. because the internal temperature of theexhaust system may be as high as 2600 F., or possibly higher, if a sparkplug is inoperative and a mixture of air and raw gas is expelled intothe exhaust system. However, the titania fibers, whether oxidized oroxygen deficient, have properties which render them particularlysuitable for a mufiiing system, these fibers apparently having acatalytic effect on the exhaust gases. Titania, zirconia, and zirconfibers over an inch in length and in single crystalline form have beenproduced in quantities according to a process set forth in a copendingapplication of Russell, Morgan, and Schefiier, Serial No. 31,964, filedon or about May 26, 1960, now Patent No. 3,065,091.

We claim:

1. A mufiiing system component comprising a casing forming an elongatechamberhaving an inlet opening and an outlet opening, and an integralcoating within said chamber forming a passage for exhaust gases betweensaid inlet opening and said outlet opening, said coating beinginterposed between said passage and said casing with the inner surfaceof said coating being substantially unobstructed for contact withexhaust gases flowing through said component, said coating comprisinghighly refractory, inorganic, crystalline fibers selected from the groupconsisting of titania, zirconia, and zircon, and an inorganic binder.

2. A mufiling system component comprising a casing forming an elongatechamber having an inlet opening and an outlet opening, and an integral,porous coating within said chamber forming a passage for exhaust gasesbetween said inlet opening and said outlet opening, said porous coatingbeing interposed between said passage and said casing with the innersurface of said coating being substantially unobstructed for contactwith exhaust gases flowing through said component, said porous coatingcomprising highly refractory, inorganic, titania fibers, and aninorganic binder holding said fibers together and forming a multiplicityof voids in said coatmg.

References Cited by the Examiner UNITED STATES PATENTS 2,065,343 12/1936Moore et al. 181-50 2,072,961 3/1937 Nelson. 2,523,260 9/1950 Campbell181-50 2,654,136 10/1953 Harford et al 252-62 X 2,811,457 10/1957 Speilet a1. 2,833,620 5/1958 Gier et al. 252-62 X 2,837,169 6/1958 Sawyer181-36 2,848,349 8/1958 Rechter et al. 106-57 X 2,884,380 4/1959 Cook etal. 252-62 2,938,937 5/ 1960 Shenk. 2,981,057 4/ 1961 Buttler 181-62 X2,991,200 7/1961 Sheridan et al. 106-57 X 3,043,094 7/1962 Nichols.3,061,416 10/ 1962 Kazokas 181-36 3,065,091 11/1962 Russell et al.106-57 X 3,110,545 11/1963 Beasley et a1 252-62 X FOREIGN PATENTS654,685 12/ 1937 Germany.

679,940 9/ 1952 Great Britain.

961,667 11/ 1949 France.

LEO SMILOW, Primary Examiner.

1. A MUFFLING SYSTEM COMPONENT COMPRISING A CASING FORMING AN ELONGATECHAMBER HAVING AN INLET OPENING AND AN OUTLET OPENING, AND AN INTEGRALCOATING WITHIN SAID CHAMBER FORMING A PASSAGE FOR EXHAUST GASES BETWEENSAID INLET OPENING AND SAID OUTLET OPENING, SAID COATING BEINGINTERPOSED BETWEEN SAID PASSAGE AND SAID CASING WITH THE INNER SURFACEOF SAID COATING BEING SUBSTANTIALLY UNOBSTRUCTED FOR CONTACT WITHEXHAUST GASES FLOWING THROUGH SAID COMPONENT, SAID COATING COMPRISINGHIGHLY REFRACTORY, INORGANIC, CRYSTALLINE FIBERS SELECTED FROM THE GROUPCONSISTING OF TITANIA, ZIRCONIA, AND ZICRON, AND AN INORGANIC BINDER.